DESCRIPTION (adapted from the abstract)In some urodeles, following lentectomy a new lens regenerats by the transdifferentiation of dorsal iris pigment epithelial cells (PECs). In culture, ventral PECs as well as PECs from other animals are able to transdifferentiate into a lens. The investigator proposes to use these systems to continue his studies of gene expression during lens regeneration. He has thus far identified several genes including homeobox-containing genes, fibroblast growth factor receptor-1 and Sonic hedgehog. He proposes to continue with studies on gene regulation of retinoblastoma and retinoic acid receptors. He also proposes to study induction of lens regeneration from the ventral iris in newts and from the dorsal iris of animals incapable of lens regeneration. This will be done by transfecting the gene of interest in the ventral or dorsal iris cells. These in vivo studies will be supplemented by in vitro ones to provide a more accurate picture of the mechanisms. Understanding induction of lens regeneration would be of enormous importance in pathological states where the lens must be removed.